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Biomedical subjects

R M Ruprecht

Publications and source records attributed to R M Ruprecht.

At least 37 records · Page 2Linked to original sources
PubMed1999

Persistent infection of rhesus macaques by the rev-independent Nef(-) simian immunodeficiency virus SIVmac239: replication kinetics and genomic stability.

We generated previously a Nef(-), replication-competent clone of SIVmac239 in which the Rev protein and the Rev-responsive element were replaced by the constitutive transport element (CTE) of simian retrovirus type 1 (A. S. von Gegerfelt and B. K. Felber, Virology 232:291-299, 1997). In the present report, we show that this virus was able to infect and replicate in rhesus macaques. The Rev-independent Nef(-) simian immunodeficiency virus induced a persistent humoral immune response in all monkeys, although viral loads were very low. Upon propagation in the monkeys, the genotype remained stable and the virus retained its in vitro growth characteristics. The infected monkeys showed normal hematological values and no signs of disease at more than 18 months post-virus exposure. Therefore, replacement of the essential Rev regulation by the CTE generated a virus variant that retained its replicative capacity both in vitro and in vivo, albeit at low levels.

Animals↗
PubMed1998

Inhibition of HIV-1 replication by an aqueous extract of Spirulina platensis (Arthrospira platensis).

An aqueous extract of the blue-green filamentous algae Arthrospira platensis (previously called Spirulina platensis) inhibited HIV-1 replication in human T-cell lines, peripheral blood mononuclear cells (PBMC), and Langerhans cells (LC). Extract concentrations ranging between 0.3 and 1.2 microg/ml reduced viral production by approximately 50% (50% effective concentration [EC50]) in PBMCs. The 50% inhibitory concentration (IC50) of extract for PBMC growth ranged between 0.8 and 3.1 mg/ml. Depending on the cell type used, therapeutic indices ranged between 200 and 6000. The extract inactivated HIV-1 infectivity directly when preincubated with virus before addition to human T-cell lines. Fractionation of the extract revealed antiviral activity in the polysaccharide fraction and also in a fraction depleted of polysaccharides and tannins. We conclude that aqueous A platensis extracts contain antiretroviral activity that may be of potential clinical interest.

Cell Line↗
PubMed1998

Synergistic neutralization of simian-human immunodeficiency virus SHIV-vpu+ by triple and quadruple combinations of human monoclonal antibodies and high-titer anti-human immunodeficiency virus type 1 immunoglobulins.

We have tested triple and quadruple combinations of human monoclonal antibodies (MAbs), which are directed against various epitopes on human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins, and a high-titer anti-HIV-1 human immunoglobulin (HIVIG) preparation for their abilities to neutralize a chimeric simian-human immunodeficiency virus (SHIV-vpu+). This virus encodes the HIV-1 strain IIIB env, tat, rev, and vpu genes. The quantitative nature of the Chou-Talalay method (Adv. Enzyme Regul. 22:27-55, 1984) allows ranking of various combinations under identical experimental conditions. Of all triple combinations tested, the most potent neutralization was seen with MAbs 694/98D plus 2F5 plus 2G12 (directed against domains on V3, gp41, and gp120, respectively) as measured by the total MAb concentration required to reach 90% neutralization (90% effective concentration [EC90], 2.0 microg/ml). All triple combinations involving MAbs and/or HIVIG that were tested yielded synergy with combination index values of < 1; the dose reduction indices (DRIs) ranged from 3.1 to 26.2 at 90% neutralization. When four MAbs (the previous three plus MAb F105, directed against the CD4 binding site) were combined, higher neutralization potency (EC90 1.8 microg/ml) and a higher degree of synergy compared to any triple combination were seen. The mean DRIs of the quadruple combination were approximately twice that of the most synergistic triple combination. We conclude that human MAbs targeting different HIV-1 envelope glycoprotein epitopes exhibit strong synergy when used in combination, a fact that could be exploited clinically for passive immunoprophylaxis against HIV-1.

Animals↗
PubMed1998

Oral SIV, SHIV, and HIV type 1 infection.

Several strains of simian immunodeficiency virus (SIV), including uncloned and molecularly cloned SIV strains, can cross intact mucosal surfaces after oral exposure in both adult and neonatal rhesus macaques, resulting in viremia and disease. Cell-free SIV strains as well as infected whole blood have resulted in systemic infection after oral inoculation. Neonatal macaques, exposed orally to the chimeric SHIV-vpu+, a derivative of SIVmac239 that encodes the env gene of the T cell-tropic HIV-IIIB, have also become persistently infected. These data indicate that oral exposure to various virus strains, including T cell-tropic variants, leads to infection. After nontraumatic inoculation, the oral route was more efficient than the rectal route in permitting SIV entry in adult macaques. Infection and AIDS resulting from oral exposure of adult macaques have implications for the transmission of the human immunodeficiency virus type 1 (HIV-1) during oral-genital contact.

AIDS Vaccines↗
PubMed1997

Phylogenetic relationship of the complete Rauscher murine leukemia virus genome with other murine leukemia virus genomes.

We report the complete nucleotide sequence of the genome of Rauscher murine leukemia virus (R-MuLV), the replication-competent helper virus present in the Rauscher virus complex, and its phylogenetic relationship with other murine leukemia virus genomes. An overall sequence identity of 97.6% was found between R-MuLV and the Friend helper virus (F-MuLV), and the two viruses were closely related on the phylogenetic trees constructed from either gag, pol, or env sequences. Moloney murine leukemia virus (Mo-MuLV) was the next closest relative to R-MuLV and F-MuLV on all trees, followed by Akv and radiation leukemia virus (RadLV). The most distantly related helper virus was Hortulanus murine leukemia virus (Ho-MuLV). Interestingly, Cas-Br-E branched with Mo-MuLV on the gag and pol trees, whereas on the env tree, it revealed the highest degree of relatedness to Ho-MuLV, possibly due to an ancient recombination with an Ho-MuLV ancestor. In summary, a phylogenetic analysis involving various MuLVs has been performed, in which the postulated close relationship between R-MuLV and F-MuLV has been confirmed, consistent with the pathobiology of the two viruses.

Algorithms↗
PubMed1997

Detection of simian T cell leukemia virus type I infection in seronegative macaques.

Simian species of Asian and African origin are naturally infected with the simian T cell leukemia virus type I (STLV-I). Like the closely related human T cell leukemia virus type I (HTLV-I), STLV-I is primarily cell associated, and typical infections exhibit low viral burdens. Four macaques experimentally inoculated with a new STLV-I strain isolated from a sooty mangabey monkey were examined over extended periods of time for signs of infection by (1) commercial enzyme immunoassay and immunoblot assay for cross-reactive serum antibodies to HTLV-I, (2) commercial HTLV-I p24gag antigen-capture assay on supernatants from cocultures of macaque peripheral blood mononuclear cells (PBMCs) with human PBMCs, and (3) nested PCR amplification of proviral sequences in macaque PBMC DNA. The nested PCR assay was 100% specific and detected a single STLV-I copy in 150,000 PBMCs. In addition, our data show that experimental infection of macaques with STLV-I can be serologically silent for more than 43 months.

Animals↗
PubMed1997

Human immunodeficiency virus-1 entry into purified blood dendritic cells through CC and CXC chemokine coreceptors.

Blood dendritic cells (DC) are susceptible to both macrophage (M) and T-cell line (T) tropic human immunodeficiency virus type 1. The CC chemokines RANTES, macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, eotaxin, and, to a lesser extent, monocyte chemoattractant protein-1 (MCP-1) and MCP-4 blocked entry of M-tropic virus into blood DC. The CXC chemokine, SDF-1, a fusin (CXCR4 chemokine receptor) ligand, and an antifusin antibody inhibited DC entry by T-tropic virus. Purified blood DC contained CCR1, CCR2, CCR3, and CCR5 as well as the CXCR4 chemokine receptor RNA transcripts and high levels of fusin on the cell surface. The coexpression of multiple chemokine receptors offers a molecular mechanism to explain the permissiveness of DC for both M- and T-tropic viruses.

Chemokine CCL11↗
PubMed1997

Synergistic neutralization of a chimeric SIV/HIV type 1 virus with combinations of human anti-HIV type 1 envelope monoclonal antibodies or hyperimmune globulins.

A panel of 14 human IgG monoclonal antibodies (MAbs) specific for envelope antigens of the human immunodeficiency virus type 1 (HIV-1), 2 high-titer human anti-HIV-1 immunoglobulin (HIVIG) preparations, and 15 combinations of MAbs or MAb/HIVIG were tested for their ability to neutralize infection of cultured human T cells (MT-2) with a chimeric simian immunodeficiency virus (SHIV-vpu+), which expressed HIV-1 IIIB envelope antigens. Eleven MAbs and both HIVIGs were neutralizing. When used alone, the anti-CD4-binding site MAb b12, the anti-gp41 MAb 2F5, and the anti-gp120 MAb 2G12 were the most potent. When combination regimens involving two MAbs targeting different epitopes were tested, synergy was seen in all paired MAbs, except for one combination that revealed additive effects. The lowest effective antibody concentration for 50% viral neutralization (EC50) and EC90 were achieved with combinations of MAbs b12, 2F5, 2G12, and the anti-V3 MAb 694/98D. Depending on the combination regimen, the concentration of MAbs required to reach 90% virus neutralization was reduced approximately 2- to 25-fold as compared to the dose requirement of individual MAbs to produce the same effect. Synergy of the combination regimens implies that combinations of antibodies may have a role in passive immunoprophylaxis against HIV-1. The ability of SHIV to replicate in rhesus macaques will allow us to test such approaches in vivo.

Animals↗
PubMed1997

Simultaneous detection of simian retrovirus type D serotypes 1, 2, and 3 by polymerase chain reaction.

Asymptomatic infection of macaques with macaques with simian retroviruses type D (SRV/D), the etiologic agents of one form of retrovirus-induced simian immunodeficiency disease, can confound experiments with the simian immunodeficiency virus (SIV), which also induces immunodeficiency disease in macaques. The SIV/macaque model is the preferred nonhuman primate model for AIDS-related research. Serological screening for SRV/D alone is insufficient because not all infected animals seroconvert, and virus isolation by cocultivation may require 4 to 6 weeks. We have established a DNA polymerase chain reaction (PCR) assay. One set of nested primers allows detection of SRV/D serotypes 1, 2, and 3 and distinguishes SRV-2 from the other two serotypes. The PCR assay is sensitive; a single proviral copy of SRV/D could be detected in 150,000 to 210,000 macaque peripheral blood mononuclear cells (PBMCs). When applied to a panel of virus isolation-positive macaque samples, the PCR assay was positive in 100% of the tests. No false-positive results were seen when known specific-pathogen-free (SPF) macaques were examined. We propose that macaques be screened with a combination of SRV/D serology and this DNA PCR assay prior to enrollment in experiments with SIV.

Animals↗
PubMed1996

Neutralizing and infection-enhancing antibody responses do not correlate with the differential pathogenicity of SIVmac239delta3 in adult and infant rhesus monkeys.

Variants of SIV containing a deletion in the nef gene are attenuated in adult macaques, where they provide protection from challenge with pathogenic SIV, but the mechanism of protection remains unknown. One of these attenuated variants carrying deletions in nef, vpr, and NRE (SIVmac239delta3) was recently found to be pathogenic in infant macaques exposed to the virus at birth. We investigated whether inadequate or inappropriate antiviral humoral immune responses could explain why this virus causes disease in infant macaques. Plasma samples from four infants infected with SIVmac251 and five infants and two adults infected with SIVmac239delta3 were evaluated for neutralizing Abs to a laboratory-passaged stock of SIVmac251, an animal challenge stock of SIVmac239/nef-open, and a stock of SIVmac239delta3 to which animals were exposed. Plasma samples were evaluated further for complement-mediated Ab-dependent enhancement (C'-ADE) of SIVmac239/nef-open in vitro. High-titer neutralizing Abs to SIVmac251 were detected in plasma samples from adults and most infants within 3 to 5 wk of infection with either virus. Neutralizing Abs to SIVmac239/nef-open and SIVmac239delta3 developed more slowly, being undetectable before 23 to 63 wk of infection. Timing, magnitude, and breadth of neutralizing Ab responses did not correlate with progression to disease or lack thereof and gave no indication of an impaired humoral immune response in infants. Furthermore, C'-ADE was detected equally in plasma samples from adults and infants. The results indicate that infection with SIVmac239delta3 causes disease in infant macaques despite their mounting of antiviral humoral immune responses comparable to those of adults.

Age Factors↗
PubMed1996

Infection and AIDS in adult macaques after nontraumatic oral exposure to cell-free SIV.

Unprotected receptive anal intercourse is a well-recognized risk factor for infection with human immunodeficiency virus-type 1 (HIV-1). Isolated human case reports have implicated HIV-1 transmission by oral-genital exposure. Adult macaques exposed nontraumatically to cell-free simian immunodeficiency virus (SIV) through the oral route became infected and developed acquired immunodeficiency syndrome (AIDS). The minimal virus dose needed to achieve systemic infection after oral exposure was 6000 times lower than the minimal dose required to achieve systemic infection after rectal exposure. Thus, unprotected receptive oral intercourse, even in the absence of mucosal lesions, should be added to the list of risk behaviors for HIV-1 transmission.

Animals↗
PubMed1996

Murine and simian retrovirus models: the threshold hypothesis.

By considering the dynamic relationship between retroviruses and their hosts, we have developed a unifying hypothesis to explain such disparate clinical phenomena as differential pathogenicity of a given virus in adults and neonates, transient infection with clearance of provirus-containing cells, long-term non-progression and vaccine effects of fully pathogenic viruses. The threshold hypothesis predicts that an opportunity exists during acute retroviral infection to influence the ultimate clinical outcome: if virus replication is kept below threshold by any means, including drug therapy or passive immunoprophylaxis with neutralizing antibodies, the host will prevail and win the race.

Animals↗
PubMed1996

Synergy, activity and tolerability of zidovudine and interferon-alpha in patients with symptomatic HIV-1 infection: AIDS Clincal Trial Group 068.

Thirty-four subjects with symptomatic HIV-1 infection, p24 antigenaemia, and CD4 cell counts > 200/mm3 were randomly assigned to receive treatment with either zidovudine (ZDV) orally, interferon-alpha (IFN-alpha) subcutaneously, or both at respective low (200 mg ZDV/ 2 million international units IFN-alpha (MIU)), middle (400 mg/4 MIU) or high (600 mg/6 MIU) daily dose levels for 12 weeks. Thereafter, all patients received combination therapy at the initially assigned dose level to a total of 96 weeks. This design permitted analysis by the combination index (CI) method, which demonstrated antiretroviral synergy between ZDV and IFN-alpha with respect to p24 antigen suppression. Over the first 12 weeks, combination therapy was acceptably tolerated, more so than IFN-alpha monotherapy, and it was significantly more active in suppressing antigenaemia than either of the monotherapies. Similarly, the high-dose combination was the most active dose level over weeks 12 to 96. Combination ZDV/IFN-alpha at the optimal dose level defined by this trial merits further study. In addition, the CI design strategy employed here may be useful for the investigation of new antiretroviral combinations.

Administration, Cutaneous↗